When interfacing with an input output (I/O) device, an I/O interface is used. So that the I/O interface may communicate properly with the I/O device, a certain output voltage swing is typically desired. This voltage swing may be provided by a device driver situated within the I/O interface. The device driver may be in the form of a microprocessor device.
Microprocessor devices typically are powered by voltage supplies that may provide, for example, a voltage swing between 0 and VDD. This voltage swing between 0 and VDD may be different than the voltage swing requirements of the device to which the interface is coupled. For example, the I/O device may desirably rely upon a voltage swing between 0 and OVDD volts.
If the microprocessor voltage swings between 0 and VDD and the device relies upon a voltage swing between 0 and OVDD, a conversion is desirably required so that the microprocessor and the device driver may communicate. In some cases, the difference between VDD and OVDD may be as much as two times that of VDD. For example, the VDD voltage may be 2.5 volts or 3.3 volts while the OVDD voltage may be 5 volts. In another example, the VDD voltage may be 1.8 volts while the OVDD voltage may be 3.3 volts.
To enable a device driver with a voltage swing between 0 and VDD to operate with an output device which desirably expects a voltage swing between 0 and OVDD, a translation circuit may be used. An exemplary translation circuit is described, for example, in U.S. Pat. No. 5,300,835 to Assar et al. As set forth in the aforementioned patent, it is known to use together a variety of components with different voltage swings. Various circuits for performing these conversions are well known in the art. However, some of these circuit designs may result in undesirably slow signal throughput. In other designs, DC power may be disadvantageously burned as the signal swing translation is occurring. This may be undesirable in situations where power conservation is desired.